The potential allergens in Moringa oleifera leaf proteins functionally activate murine bone marrow-derived dendritic cells and induce their differentiation toward a Th2-polarizing phenotype

BACKGROUND Moringa oleifera leaves are an inexpensive substitute for staple foods. Despite limited data, Moringa oleifera leaf protein (Mo-Pr) may be allergenic in BALB/c mice. In mouse models and allergic patients, dendritic cells (DCs) may be involved in food allergy. In addition, some allergens, including food allergens, can directly activate DCs and induce Th2 polarization. We investigated whether Mo-Pr can modulate the functional profile of murine BMDCs in vitro. MATERIALS AND METHODS BMDCs were obtained from mouse bone marrow cultured with GM-CSF for 7 days and then treated with LPS or Mo-Pr. BMDC phenotypes were evaluated by flow cytometry, cytokine production by ELISA, expression of key genes and receptors by flow cytometry or qRT-PCR, effects on T-cell differentiation by MLR, Mo-PR-specific IgE in recipient serum after BMDC transfer, and transcriptional changes in BMDCs by RNA-Seq. RESULTS Mo-Pr treatment significantly induced BMDC maturation, increased expression of surface costimulatory molecules CD80/86 and MHCⅡ, production of IL-12 and TNF-α, and induction of T-cell differentiation. Mo-Pr treatment stimulated BMDC expression of the Th2 promoters OX40L and TIM-4, induced production of the Th2-type chemokines CCL22 and CCL17, and decreased the Th1/Th2 ratio in vitro. Healthy recipients of Mo-Pr-treated BMDCs produced Mo-Pr-specific IgE. CONCLUSIONS Mo-Pr functionally activates murine BMDCs and induces differentiation toward a Th2-polarizing phenotype. Mo-Pr can bind to the C-type lectin receptor DC-SIGN to activate the MAPK pathway and polarize BMDCs toward a Th2-polarizing phenotype.